In the effort to expand the spectrum of probiotic strains, the investigation of probiotic potential in enhancing gut microbiota health and strengthening the immune system is foundational for a better understanding of the probiotic concept and the development of new probiotic products. This thesis investigates the probiotic and postbiotic potential of the Kluyveromyces marxianus DS12 strain, evaluating a range of functional parameters important for its application in probiotic formulations. The antimicrobial properties of the strain were tested against a broad spectrum of pathogens, and its ability to form biofilms, crucial for survival and colonization in the gut conditions, was analyzed. Auto-aggregation and co-aggregation characteristics were assessed to determine the strain's interaction with the gut microbiota, and antioxidant potential was examined through the ability to neutralize DPPH free radicals. Hemolytic activity and response to oxidative stress were also determined, as well as the strain's ability to maintain viability in simulated gastrointestinal conditions. The results of these comprehensive analyses provide a basis for the further application of the K. marxianus DS12 strain as a probiotic agent in functional foods and therapy. The outcomes of the conducted experiments confirm that the Kluyveromyces marxianus DS12 strain possesses promising characteristics needed for a quality probiotic candidate, and with further in-depth analyses, its potential for postbiotic applications is also highlighted.